Tensile Stress In Concrete Ringwall

[PEStructural]

I am designing an AWWA D100 circular steel tank that is supported on a concrete ringwall. I am designing the anchorage to the tank using ACI 318-02 Appendix D "Anchoring To Concrete". When designing for pullout strength ( Section D.5.3 ), there is a variable Y4. It then gives a stipulation "For an anchor located in a region of a concrete member where analysis indicates no cracking ( ft < fr ) at service load levels, the following modification factor shall be permitted, Y4 = 1.4".

I have the hoop tension in the concrete ringwall calculated.

My question is to get the tensile stress, ft, do I divide the hoop tension by the gross area of the ringwall because it is all in tension?

Any help is greatly appreciated

 

[jec67]

For the ringwall, the tension will be divided by the gross area to determine the tensile stress in the concrete, provided that the loads acting downward are colinear with the loads acting upward. Otherwise, one will get a torsional moment on the ring.

Typically, the tensile strength of the concrete is ignored for the ringwall design, and the rebar is designed to take the full hoop tension.